1. Field of the Invention
The present invention relates to a shoe sole having reinforced structure.
2. Description of the Related Art
It is well known to have a reinforcing member in the arch portion of the sole of a shoe conforming to the shape of the treadless portion of the midsole, i.e., the portion of the midsole not attached to an outer sole that does not have ground contact when the outer sole is grounded. Such reinforcing device reinforces the rigidity of the treadless portion of the midsole by suppressing the deformation of the midsole. These known devices are exemplified those shown in FIGS. 6(a) and 6(b) and FIGS. 7(a) and 7(b), herein.
FIG. 6(a) exemplifies the side elevation of a prior art shoe sole disclosed in the Japanese Laid-Open Utility Model Publication (unexamined) No. 7-34703 (Published on Jun. 27, 1995). FIG. 6(b) is the bottom view of such prior art shoe sole. In this prior art shoe sole, the reinforcing member 3 of the treadless portion of the midsole is an integrally formed member that includes an arch portion 3a, a front support portion 30 at the front end of the sole and a rear support portion 31 at a rear end of the sole. The arch portion 3a is affixed on its back face to the midsole 2. The front support portion 30 and the rear support portion 31 are disposed, respectively, at the front and rear of the arch portion 3a. The front support portion 30 is sandwiched between the midsole 2 and an outer sole 1 below the midsole 2. The front support portion 30 is supported on a front supporting face 1F of the upper surface of the outer sole 1. The rear support portion 31 is sandwiched between the midsole 2 and the outer sole 1. The rear support portion 31 is supported on a rear supporting face 1B of the upper face of the outer sole 1.
FIG. 7(a) exemplifies the side elevation of another prior art shoe sole as disclosed in the Japanese Patent Publication (unexamined) No. 7-79804 (Published on Mar. 28, 1995). FIG. 7(b) is a bottom side perspective view of such prior art shoe sole. This sole is substantially similar to the aforedescribed prior art sole.
Additionally, the reinforcing device 3 is made of a sufficiently soft or flexible material to permit the shoe sole to have a torsional motion. Because of this, the front support portion 30 and the rear support portion 31 of the reinforcing device 3 can displace longitudinally upon the grounding of the sole. This can cause the reinforcing device 3 to longitudinally extend, flattening the arch portion 3a of the reinforcing device 3. This causes the treadless portion of the midsole 2 to depress toward the ground causing stress on the arch of the foot.